Solar heat receiver

ABSTRACT

Heat-receiving pipes of a heat receiver have portions having high heat flux on at the side near an opening in a length direction and extending to positions outside of a casing in a radial direction. Expanded sections having an expanded pitch circle diameter constituted by the plurality of heat-receiving pipes are formed, and a heat input quantity per unit area of the heat-receiving pipe is decreased in the portions near the opening.

FIELD OF THE INVENTION

The present invention relates to a solar heat receiver for increasing atemperature of a fluid medium that drives a turbine of a solar heatpower generator.

BACKGROUND ART

In recent years, in terms of prevention of global warming andsuppression of the use of fossil fuels, power generation using cleanenergy such as natural energy having less harmful emissions such ascarbon dioxide and nitrogen oxides, and recycled energy reusing theresources has received attention. The clean energy exceeds a certainamount of electrical energy required by the whole world. However, withregard to energy distribution of clean energy, effective energy (energythat may be externally taken and utilized) over a wide range is low. Dueto this situation, since the power generation using clean energy has lowconversion efficiency to power and high cost of power generation, such apower generation has not been sufficiently propagated. Thus, as thepower generation type, power generation through solar thermal energyusing power generation techniques such as gas turbines, steam turbines,and a gas turbine combined cycle (GTCC) is expected (for example, seePatent Document 1).

And now, in the use of solar thermal energy, normally, the lightcondensation and the heat collection are performed by a combination of alight condenser using a mirror and a heat receiver. As a combinationmethod of the light condenser and the heat receiver, generally, thereare two kinds of methods including a trough light condensation methodand a tower light condensation method.

The trough light condensation method is a method in which solar light isreflected by a semi-cylindrical mirror (a trough), light and heat arecollected in a pipe passing through a center of the cylinder, and thetemperature of a thermal medium passing in the pipe is increased.However, in the trough light condensation method, the direction of themirror is changed so as to track the solar light, but since the controlof the mirror is one-axis control, it is difficult to expect a hightemperature rise of the thermal medium.

On the other hand, the tower light condensation method is a method inwhich a light condensation heat receiver is arranged on a tower section(a support section) erected from the ground, a plurality of focusingreflected light control mirrors called a heliostat (a solar lightcondensation system) are arranged so as to surround the tower section,and the solar light reflected in the heliostat is guided to the lightcondensation heat receiver to perform light condensation and heatcollection. Recently, in terms of further improving the efficiency ofthe power generation cycle, with regard to the thermal medium subjectedto the heat exchange by the light condensation heat receiver,development of a power generator (a tower light condenser) of the towerlight condensation type capable of further raising the temperature hasbeen actively carried out.

PRIOR ART DOCUMENT Patent Document

-   [Patent Document 1] Japanese Patent No. 2951297

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, in the heat receiver of the related art, the following problemhas occurred.

That is, in the heat exchanger in the tower light condenser of therelated art, the temperature of a fluid is raised by causing the fluidto flow through a plurality of heat-receiving pipes arranged on an innersurface of a cylindrical insulating container, irradiating the surfaceof the heat-receiving pipe with sunlight, and inputting heat. However,in this case, a difference in temperature is increased between a frontsurface of the heat-receiving pipe on which sunlight is directlyincident and a back surface facing a wall side. Particularly, when themirrors are arranged to be axially symmetrical, a heat load near anentrance of the heat-receiving pipe is increased by the area effect ofthe mirrors when the light is condensed and the temperature isincreased. Furthermore, the temperature difference is generated betweenthe front surface and the back surface of the heat-receiving pipe due tocycles of day and night, influence of clouds or a fluctuation in anirradiated amount of sunlight. As such, there is a drawback that thermalfatigue is easily generated particularly in the heat-receiving pipe nearthe entrance having a high temperature and a large temperaturedifference, durability of the heat-receiving pipe is required, and thereis thus room for improvement at this point.

The present invention has been achieved in view of the abovecircumstances, and it is an object of the present invention to provide asolar heat receiver that is able to improve a life strength of theheat-receiving pipe by reducing a temperature difference between frontand back surfaces (a front portion and a back portion in an incidentdirection of sunlight) of the heat-receiving pipe.

Means for Solving the Problem

In order to achieve the object mentioned above, a solar heat receiveraccording to the present invention includes a casing having an openingon which sunlight is incident, and a plurality of heat-receiving pipeswhich are arranged in the casing in a circumferential direction of thecasing and through which a heat medium is circulated. The heat-receivingpipes are configured so that portions having high heat flux on theopening side are extended to a radially outer position of the casing andexpanded sections constituted by a plurality of heat-receiving pipes andhaving an expanded pitch circle diameter are formed.

The solar heat receiver according to the present invention is normallyused in tower type solar heat power generation. The solar heat receiveraccording to the present invention includes a casing having an openingon which sunlight is incident, and a plurality of heat-receiving pipesthat are vertically arranged inside the casing and raise the temperatureof the heat medium flowing therein by the irradiation of the sunlight.The plurality of heat-receiving pipes are arranged so as to be spacedfrom each other and to extend in one direction. Centers of theheat-receiving pipes are arranged on the same circumference. Theplurality of heat-receiving pipes may be bent outward in a radialdirection in a portion near the opening of the casing. Thus, a circlepassing through the centers of the plurality of heat-receiving pipes isconfigured so that a diameter in a region near the opening is expandedcompared to a diameter in a region separated from the opening.

Herein, the pitch circle in the present invention is a circle whichintersects center axes of the plurality of heat-receiving pipes throughthe centers of the heat-receiving pipes. That is, the plurality ofheat-receiving pipes are arranged at a predetermined pitch (a space),and the centers thereof are arranged on the circumference of the pitchcircle.

In the present invention, by expanding the diameter of the pitch circlein a portion of the heat-receiving pipe having high heat flux, surfaceareas of the heat-receiving pipe and a heat insulating material areincreased in that portion, and thus it is possible to reduce a heatinput quantity per unit area to the heat-receiving pipe. Moreover, thereduced amount of heat in the heat-receiving pipe enters from aninterval between the heat-receiving pipes to the heat insulatingmaterial of the back side, and heat is further diffused to thesurrounding.

That is, sunlight, which is incident on the opening of the casing andpasses between the heat-receiving pipes, is incident on a wall surfaceof the casing separated from the opening of the casing behind theheat-receiving pipe. Moreover, the heat insulating material or a heatabsorption material forming the inner wall surface of the casing isheated by sunlight passing between the heat-receiving pipes. The heatedheat insulating material or the heat absorption material radiates heat,and heats the portion of the back side of the heat-receiving pipe towhich sunlight is not directly irradiated.

According to the present invention, the interval between theheat-receiving pipes in the portion of the heat-receiving pipe havinghigh heat flux near the opening of the casing is widened, and the numberof the heat-receiving pipes arranged per unit area is reduced.Simultaneously, a distance between the heat-receiving pipe and theopening of the casing, in which a diameter of luminous flux of sunlightis minimized, is separated, and energy of sunlight directly irradiatedper unit area of the surface of the heat-receiving pipe is reduced.Thus, in a region near the opening, more sunlight than in the pastpasses between the heat-receiving pipes, and energy of sunlight directlyirradiated to the heat-receiving pipe is reduced. For this reason, theheat flux of the heat-receiving pipes may be reduced compared to therelated art in the region near the opening of the casing.

In this manner, the heat flux of the heat-receiving pipe surface isreduced in a region in which the heat flux of the heat-receiving pipe iseasily increased near the opening of the casing, and thus it is possibleto reduce the temperature difference between the front surface (asurface of the center axis side of the casing) and the back surface (asurface of an inner surface side of the casing) of the heat-receivingpipe. That is, the temperature difference is reduced between a portionof the front side of the heat-receiving pipe to which sunlight incidentfrom the opening of the casing is directly irradiated and a portion ofthe back side of the heat-receiving pipe to which sunlight incident fromthe opening of the casing is not directly irradiated. Accordingly, lifestrength of the heat-receiving pipe may be extended.

Furthermore, in the solar heat receiver according to the presentinvention, the diameter of the heat-receiving pipe in the expandedsection may be greater than that of the heat-receiving pipe in a portionother than the expanded section. That is, in a region in which thediameter of the circle passing through the centers of the heat-receivingpipes is expanded, the diameters of each heat-receiving pipe may beexpanded compared to the diameters of each heat-receiving pipe in otherregions.

In the present invention, by increasing the diameter of theheat-receiving pipe in the region in which the diameter of the circlepassing through the center of the heat-receiving pipe is expanded or theexpanded section of the heat-receiving pipe, the surface area of theouter circumferential surface of the heat-receiving pipe is furtherexpanded. Thus, it is possible to increase the amount of heat exchangebetween the heat medium flowing in the heat-receiving pipe and theheat-receiving pipe, and thus the length of the heat-receiving pipe maybe shortened. Accordingly, it is possible to further reduce thetemperature difference between the portion (the front surface) of thefront side of the heat-receiving pipe to which sunlight is directlyincident and the portion (the back surface) of the back side to whichsunlight is not directly incident.

Furthermore, by expanding the diameter of the heat-receiving pipe asmentioned above, the volume of the heat medium in the heat-receivingpipe is increased. Thus, the heat medium in the heat-receiving pipe isincreased in heat capacity, the temperature is not easily increased, andthe temperature of the heat-receiving pipe is not easily increased.Thus, it is possible to further reduce the temperature differencebetween the front portion of the heat-receiving pipe and the backportion thereof in the incident direction of sunlight.

Furthermore, in the solar heat receiver according to the presentinvention, a heat transfer accelerator may be equipped inside theheat-receiving pipe in the expanded section. That is, in a region inwhich the diameter of the circle passing through the centers of theplurality of heat-receiving pipes is expanded, the heat transferaccelerator having a thermal conductivity higher than that of theheat-receiving pipe may be placed inside the heat-receiving pipe.Furthermore, thermal conductivity of the heat transfer accelerator maybe higher than that of the heat medium.

According to the present invention, it is possible to increase the heattransfer coefficient inside the heat-receiving pipe and more effectivelytransfer heat from the heat-receiving pipe to the heat medium. Thus,since the amount of heat transfer between the heat-receiving pipe andthe heat medium may be increased, length dimensions of theheat-receiving pipes may be shortened, and thus the size of the heatreceiver may be reduced. Furthermore, when the diameter of theheat-receiving pipe is expanded in the expanded section or the region inwhich the diameter of the circle passing through the centers of theplurality of heat-receiving pipes is expanded, the heat transferaccelerator may be equipped inside the heat-receiving pipe withoutincreasing the pressure loss of the inside of the heat-receiving pipecompared to other regions.

Effects of the Invention

According to the solar heat receiver of the present invention, thetemperature difference between the front portion and the back portion ofthe heat-receiving pipe may be reduced, and thus the life strength ofthe heat-receiving pipe may be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a tower type solar light condensation heatreceiver according to a first embodiment of the present invention.

FIG. 2 is a plan view showing an arrangement of heliostats around atower.

FIG. 3A is a transverse cross-sectional view showing a schematicconfiguration of the tower top.

FIG. 3B is a longitudinal cross-sectional view showing a schematicconfiguration of the tower top.

FIG. 4 is a perspective view showing a schematic configuration of a heatreceiver.

FIG. 5 is a perspective view of a heat-receiving pipe shown in FIG. 4.

FIG. 6 is a cross-sectional view taken along line A-A shown in FIG. 3Bshowing a configuration of an insulating material (a radiation shieldplate)

FIG. 7 is a perspective view that is seen from an arrow B of FIG. 6.

FIG. 8 is a longitudinal cross-sectional view showing a schematicconfiguration of the heat receiver.

FIG. 9 is a graph of solar heat incident intensity of the heat-receivingpipe shown in FIG. 8.

FIG. 10 is a longitudinal cross-sectional view showing a schematicconfiguration of a heat-receiving pipe according to a second embodiment.

MODE(S) FOR CARRYING OUT THE INVENTION

Hereinafter, a solar heat receiver of an embodiment of the presentinvention will be described with reference to the accompanying drawings.The embodiment shows an aspect of the present invention that is notlimiting to the present invention, but is able to be arbitrarily changedin the range of technical ideas. Furthermore, in the drawings below, inorder to better understand each configuration, scales, numbers or thelike are different from those of an actual structure.

First Embodiment

A tower type solar power plant shown in FIG. 1 includes a solar lightheat receiver placed on a high tower, and mirrors called heliostatswhich are placed on the ground around the solar light heat receiver andare able to control reflected light. The tower type solar power plantcondenses sunlight on the solar light heat receiver on the tower throughthe heliostats to generate electricity.

As shown in FIG. 1, a heliostat field 101 is provided on the ground G. Aplurality of heliostats 102 for reflecting sunlight are placed in theheliostat field 101. Furthermore, a tower type solar light condensationheat receiver 100 which receives sunlight guided by the heliostats 102is provided in a central section of the heliostat field 101. As shown inFIG. 2, the heliostats 102 are placed 360° around the entirecircumference of the tower type solar light condensation heat receiver100.

The tower type solar light condensation heat receiver 100 is constitutedby a tower 110 erected on the ground G, an accommodation chamber 120over the tower 110, and a heat receiver (a solar heat receiver) 10provided in the accommodation chamber 120.

A plurality of reinforcing members 111 are provided in the tower 110.The reinforcing members 111 are placed so as to intersect the tower 110in a height direction (a length direction) and are provided at intervals(distances between the reinforcing members adjacent to each other) P inthe height direction of the tower 110. The interval P is increasedtoward the top (a side provided with the heat receiver 10) of the tower10 in a range to be included in an optical path through which reflectedlight of sunlight is incident on the heat receiver 10 by the heliostat102. Accordingly, sunlight reflected by the heliostat 102 is condensedin the heat receiver 10 on the tower 110 without being blocked by thereinforcing members 111. In addition, the arrangement structure ofreinforcing members 111 may be, for example, a truss structure in termsof ensuring rigidity.

As shown in FIG. 3A, the accommodation chamber 120 of the top of thetower 110 has a circular plane shape.

As shown in FIG. 3B, the accommodation chamber 120 has two accommodationchambers including an upper accommodation chamber 121 and a loweraccommodation chamber 122. An opening 122 c for capturing sunlight isprovided on a bottom of the lower accommodation chamber 122. The planeshape of the opening 122 c is a circular shape. A diameter of theopening 122 c is determined depending on a spot diameter of sunlight.The diameter of the opening 122 c of the present embodiment is greaterthan or equal to the spot diameter of sunlight. Herein, the spotdiameter is a diameter of a position at which the diameter of luminousflux of sunlight, which is reflected by the heliostats 102 of theheliostat field 101 and is incident on the opening 122 c, is thesmallest.

As shown in FIGS. 3A and 3B, the heat receiver 10 includes a cylindricalcasing 11 and a heat-receiving pipe 20. In addition, the shape of thecasing 11 is not limited to the cylindrical shape and may be a conicalshape, a polygonal column shape, a spherical shape, an oval shape, or acombined shape of two or more of these. The heat receiver 10 is providedin the lower accommodation chamber 122. Specifically, the heat receiver10 is fixed to an upper wall 122 a of the lower accommodation chamber122 via a lifting tool 12, and is suspended from the upper wall 122 a inthe lower accommodation chamber 122. That is, the heat receiver 10 isplaced having a space between the inner walls in the position separatedfrom the inner wall of the lower accommodation chamber 122 so as not tocome into contact with the inner wall of the lower accommodation chamber122. A plurality of lifting tools 12 are provided in the circumferentialdirection of the upper wall 122 a having a circular plane shape. Thelifting tools have flexibility. Furthermore, the lifting tools 12 passthrough the casing 11. With such a configuration, in case that the heatexchange is performed between the heat-receiving pipe 20 and the heatmedium flowing in the heat-receiving pipe 20 on the inside of the heatreceiver 10, and even when the temperature of the casing 11 is increased(for example, 900° C. or more), the deformation due to the thermalexpansion of the casing 11 is allowed. Furthermore, an opening 11 b forcapturing sunlight is provided on the lower surface side (the bottom) ofthe casing 11. Like the opening 122 c mentioned above, the opening 11 bis formed to have a circular plane shape. The diameter of the opening 11b is determined depending on the spot diameter of sunlight. The diameterof the opening 11 b of the present embodiment is greater than or equalto the spot diameter of sunlight. Furthermore, the diameter of theopening 11 b of the casing 11 of the present embodiment is smaller thanor equal to the diameter of the opening 122 c of the accommodationchamber 120.

In addition, in FIG. 3B, in order to better illustrate an internalstructure, the casing 11 is drawn in a cylindrical shape of the samediameter in an axial direction. However, actually, as shown in FIGS. 4and 8, the casing 11 of the present embodiment has an expanded section11 c in which a diameter of a lower portion thereof is expanded so as towiden outward in the radial direction. That is, the diameter of a lowerpart of the casing 11 near the opening 11 b is expanded compared to thediameter of an upper part of the casing 11 separated from the opening 11b. A heat-receiving pipe main body 23 extending in an axial direction (avertical direction) of the casing 11 along an inner wall surface of theexpanded section 11 c is placed inside the expanded section 11 c.

As shown in FIG. 3B, a gas turbine 30 which is operated using fluid (theheat medium) heated by the heat receiver 10 as a working fluid, and agenerator 33 which extracts actuating energy of the gas turbine 30 aselectric power are placed inside the upper accommodation chamber 121.The gas turbine 30 has a compressor 31 which sucks and compresses fluid(for example, atmosphere) serving as the heat medium to generate acompressed fluid, and a turbine 32 which is operated using the fluidcompressed by the compressor 31 and heated by the heat receiver 10 asthe working fluid. Moreover, kinetic energy generated by the rotation ofthe turbine 32 is converted into electric energy by the generator 33 andis extracted as electric power.

Devices such as a temperature sensor which detects heat received by theheat receiver 10, an auxiliary drive device which starts the gas turbine30, a regenerative heat exchanger which performs the heat exchangebetween the working fluid and the exhaust of the turbine 32 before theworking fluid is heated by the heat receiver 10, an auxiliary combustorwhich performs auxiliary combustion of the working fluid and causes theworking fluid to flow in the turbine 32, and a vibration damper whichcancels the vibration of the generator 33 may be placed inside the upperaccommodation chamber 121 as necessary. In this manner, an installationarea of the device may be reduced by integrally placing the devices overthe tower 110.

An opening 121 b for capturing fluid (atmosphere) to be supplied to thecompressor 31 is provided on the side surface of the upper accommodationchamber 121. In addition, the opening 121 b is used to discharge theexhaust from the turbine 32 to the outside as necessary.

As shown in FIGS. 3A, 3B, 4 and 5, the heat-receiving pipe 20 has alower header pipe 21, an upper header pipe 22, and a heat-receiving pipemain body 23. The lower header pipe 21 has a ring shape and is placedbelow the casing 11. Specifically, the lower header pipe 21 is exposedto the outside of the casing 11 and is placed near the lower wall 122 bin the lower accommodation chamber 122.

A plurality of heat-receiving pipe main bodies 23 are provided insidethe casing 11 in a vertical direction between the upper header pipe 22and the lower header pipe 21. The heat-receiving pipe main bodies 23 areconnected to the upper header pipe 22 at one end thereof and areconnected to the lower header pipe 21 at the other end thereof. The heatreceiving pipe main bodies 23 raise the temperature of the working fluid(heat medium) flowing therein from the lower header pipe 21 by theirradiation of sunlight. The heated working fluid is discharged from theheat-receiving pipe main body 23 to the upper header pipe 22. Theheat-receiving pipe main bodies 23 are placed at predetermined intervals(gaps) in the circumferential direction of the upper header pipe 22 (thelower header pipe 21) (see FIGS. 6 and 7). The end portion of the heatreceiving pipe main body 23 connected to the lower header pipe 21 isexposed to the outside of the casing 11. Most of the part of theheat-receiving pipe main bodies 23 is formed in a shape (a straight lineshape) that extends straight in the axial direction (a longitudinaldirection) of the casing 11. Bending stress due to self weight is notapplied to the portion of the heat-receiving pipe main bodies 23 formedin a straight line.

Furthermore, the working fluid in the heat-receiving pipe main body 23flows from the lower header pipe 21 toward the upper header pipe 23 inone direction.

The lower header pipe 21 is an annular pipe which is inflected in a ringshape or a polygonal shape when viewed from plane, and is disposed belowthe casing 11. Specifically, the lower header pipe 21 is exposed to theoutside of the casing 11 and is placed near the lower wall 122 b in thelower accommodation chamber 122. With the configuration mentioned above,the heat-receiving pipe 20 is configured so that the upper header pipe22 is fixed to the upper wall 122 a in the lower accommodation chamber122 via the lifting tool 12, all of which are suspended from the upperwall 122 a.

An L-shaped inlet pipe 13 is connected to the lower header pipe 21. Aconnection pipe 14 is connected between the inlet pipe 13 and thecompressor 31. The connection pipe 14 is exposed to the outside of thecasing 11 and is placed along the inner wall of the lower accommodationchamber 122. The compressed fluid generated by the compressor 31 issupplied to the lower header pipe 21 via the connection pipe 14 and theinlet pipe 13. The compressed fluid (the heat medium) supplied to thelower header pipe 21 flows in the plurality of heat-receiving pipe mainbodies 23 and the upper header pipe 22, and is heated by theheat-receiving pipe main body 23 and the upper header pipe 22 heated bythermal energy of sunlight that is incident from the opening 11 b.

As shown in FIGS. 4, 6 and 7, an insulating material (a heat absorptionmaterial, a heat storage material or a radiation shield plate) 15absorbing the solar heat is provided on the inner wall surface of thecasing 11. The insulating material 15 is increased in temperature byabsorbing the heat, and radiates the heat to the back surface (theportion of the back side on which sunlight is not directly incident) ofthe heat-receiving pipe main body 23. In this manner, the portion of theback side of the heat-receiving pipe 20 is heated by the thermalradiation of the insulating material 15 and the portion of the frontside of the heat-receiving pipe 20 is heated by sunlight, and thus, theentire heat-receiving pipe 20 in the circumferential direction isheated. Furthermore, the insulating material 15 sends radiation heatgenerated from the heat-receiving pipe main body 23 back to the portion(the back surface) of the back side of the heat-receiving pipe main body23, and stably heats the heat-receiving pipe main body 23. Furthermore,the insulating material 15 reduces an amount of heat going outward fromthe heat-receiving pipe main body 23 and the upper header pipe 22.

An outlet pipe 25 is connected to the upper header pipe 22 via aplurality of connecting pipes 24. The plurality of connecting pipes 24are configured so that one ends thereof are connected to the upperheader pipe 22, and the other ends thereof are connected to the outletpipe 25. The connecting pipes 24 are placed in an X shape when viewedfrom the plane. The outlet pipe 25 is bent in the upper accommodationchamber 121, and is formed in an L shape when viewed from the planeshown in FIG. 3B. The end portion of the outlet pipe 25 opposite to theside connected to the plurality of connection pipes 24 is connected tothe turbine 32. The compressed fluid, which flows through the inside ofthe heat-receiving pipe main body 23 and the upper header pipe 22 and isheated, is supplied to the turbine 32 as the high-temperaturehigh-pressure working fluid via the connecting pipe 24 and the outletpipe 25.

As shown in FIG. 8, the heat-receiving pipe main body 23 included in theheat-receiving pipe 20 of the heat receiver 10 is configured so that theportion having high heat flux at the opening 11 b side in the lengthdirection extends to a position of the outside of the casing 11 in theradial direction, and an expanded section 20 c is formed where adiameter D of the pitch circle formed of the plurality of heat-receivingpipe main bodies 23 is expanded. That is, the diameter D of the pitchcircle of the expanded section 20 c is greater than a diameter d of apitch circle in a section 20 d other than the expanded section 20 c.Herein, the pitch circle is a circle that intersects a central axis ofeach heat-receiving pipe main body 23 through the centers of theplurality of heat-receiving pipe main bodies 23. That is, the pluralityof heat-receiving pipe main bodies 23 are arranged at predeterminedpitches (gaps) in the circumferential direction of the casing 11, andthe centers thereof are placed along the circumference of the pitchcircle.

In other words, the plurality of heat-receiving pipe main bodies 23 areplaced so as to be separated from each other in the circumferentialdirection of the casing 11 and to extend in the vertical direction. Thecenters of the heat-receiving pipe main bodies 23 are placed along thesame circumference. The plurality of heat-receiving pipe main bodies 23are bent outward in the radial direction of the casing 11 in the portioncloser to the opening 11 b than the central section of the casing 11 inthe vertical direction. Accordingly, the expanded section 20 c isprovided in the heat-receiving pipe main body 23 in a region near theopening 11 b of the casing 11. By providing the expanded section 20 c inthe heat-receiving pipe main body 23, the circle passing through thecenters of the plurality of heat-receiving pipe main bodies 23 isconfigured so that the diameter D in the region near the opening 11 b isexpanded compared to the diameter d in the region separated from theopening 11 b.

In addition, the heat-receiving pipe main body 23 corresponds to theheat-receiving pipe of the present invention.

Furthermore, in FIG. 8, the insulating material 15 shown in FIGS. 4, 6and 7 is omitted.

Specifically, the expanded sections 20 c of the heat-receiving pipe mainbodies 23 are placed along the inner surface of the expanded section 11c of the casing 11 mentioned above at predetermined intervals and form asubstantially trapezoidal shape when viewed from the side, and the lowerends thereof are projected outward from the casing 11.

FIG. 9 is a graph showing an effect of the expanded section 20 c of theheat-receiving pipe main body 23 included in the heat-receiving pipe 20,a vertical axis thereof indicates the length (a distance from theopening 11 b) X of the heat-receiving pipe main body 23, and ahorizontal axis thereof indicates a heat input quantity (solar heatincident intensity) to the heat-receiving pipe main body 23. In FIG. 9,a dotted line is a result of a case in which the expanded section 20 cis not provided in the heat-receiving pipe main body 23, and a solidline is a result of a case in which the expanded section 20 c isprovided. As shown in FIG. 8, by providing the expanded section 20 c ina high temperature section K of the heat-receiving pipe main body 23near the opening 11 b, the incident solar strength to the heat-receivingpipe main body 23 is lowered as shown in FIG. 9.

In the solar heat receiver according to the first embodiment mentionedabove, the diameter D of the pitch circle is expanded in the portionhaving high heat flux (the high temperature section K) of theheat-receiving pipe main bodies 23 included in the heat-receiving pipe20. Accordingly, the surface area of the outer circumferential surfaceof the heat-receiving pipe 20 in that portion is expanded. In otherwords, the interval between the heat-receiving pipe main bodies 23 inthe high temperature section K of the heat-receiving pipe main bodies 23near the opening 11 b of the casing 11 is widened, and the number of theheat-receiving pipe main bodies 23 to which sunlight is irradiated perunit area in the region is reduced. At the same time, the distancebetween the heat-receiving pipe main bodies 23 and the opening 11 b ofthe casing 11, in which the diameter of luminous flux of sunlight isminimal, is separated, and energy of directly irradiated sunlight perunit area of the surface of the heat-receiving pipe main bodies 23 isreduced. Accordingly, in the region near the opening 11 b, more sunlightthan in the related art passes between the heat-receiving pipe mainbodies 23, and it is possible to reduce the heat input quantity per unitarea to the heat-receiving pipe main bodies 23 (see FIG. 9). Moreover,the reduced amount of heat in the heat-receiving pipe 20 including theheat-receiving pipe main bodies 23 enters the insulating material 15(see FIGS. 6 and 7) provided behind (the back side of) theheat-receiving pipe main bodies 23 through the gap between theheat-receiving pipe main bodies 23, and the heat is further diffused tothe surroundings thereof.

In this manner, the heat flux of the surface of the heat-receiving pipemain bodies 23 is reduced, it is possible to reduce the temperaturedifference between the portion (the front surface) 20 a (the surfacefacing the central axis of the casing 11) of the front side of theheat-receiving pipe main bodies 23 and the portion (the back surface) 20b (the surface facing the inner surface of the casing 11) of the backside thereof, and thus the life strength of the heat-receiving pipe 20may be extended.

Moreover, the fluctuation of a gas temperature of the heat-receivingpipe outlet is suppressed, the set gas temperature of the outlet sidemay be stabilized, and thus the operation of the turbine may bestabilized.

Next, another embodiment of the solar heat receiver of the presentinvention will be described based on the accompanying drawings. In thepresent embodiment, the same or similar members and portions as those ofthe first embodiment mentioned above are denoted by the same referencenumerals, the descriptions thereof will be omitted, and configurationsdifferent from those of the first embodiment will be described.

Second Embodiment

As shown in FIG. 10, a heat receiver (a solar heat receiver) 10Aaccording to a second embodiment is configured so that a pipe diameterof an expanded section 20 e in the heat-receiving pipe main bodies 23included in the heat-receiving pipe 20 is greater than that of a portionother than the expanded section 20 e. That is, in a region in which thediameter of the circle passing through the center of each heat-receivingpipe main body 23 is expanded, the diameter of each heat-receiving pipemain body 23 is expanded compared to the diameter of each heat-receivingpipe main body 23 in other regions.

In this manner, by increasing the diameter of the expanded section 20 eof the heat-receiving pipe main bodies 23 included in the heat-receivingpipe 20, the surface area of the outer circumferential surface of theheat-receiving pipe 20 is further increased, and thus the heat inputquantity per unit area may be further reduced. Furthermore, by enlargingthe diameter of the heat-receiving pipe main bodies 23, the volume ofthe compressed fluid in the heat-receiving pipe main bodies 23 isincreased. Accordingly, the compressed fluid in the heat-receiving pipemain bodies 23 is increased in heat capacity, the temperature does notrise easily, and the temperature of the heat-receiving pipe main bodies23 does not rise easily either. Thus, it is possible to further reducethe temperature difference between the portion (the front surface) ofthe front side of the heat-receiving pipe main bodies 23 and the portion(the back surface) of the back side thereof to the incident direction ofsunlight.

In addition, the expanded section 20 e of the heat-receiving pipe mainbodies 23 may be equipped with a heat transfer accelerator 20 h. Thatis, the heat transfer accelerator 20 h having thermal conductivityhigher than that of the heat-receiving pipe main bodies 23 may be placedinside the heat-receiving pipe main bodies 23 in the region in which thediameter D of the circle passing through the centers of the plurality ofheat-receiving pipe main bodies 23 is expanded. Furthermore, the thermalconductivity of the heat transfer accelerator 20 h may be higher thanthat of the compressed fluid flowing in the heat-receiving pipe mainbodies 23.

According to the present embodiment, by increasing the diameter of theexpanded section 20 e of the heat-receiving pipe main bodies 23 includedin the heat-receiving pipe 20, the heat transfer accelerator 20 h may beequipped inside the heat-receiving pipe main bodies 23 withoutincreasing the pressure loss. At the same time, the heat transfercoefficient inside of the heat-receiving pipe main bodies 23 may beincreased. Accordingly, since an amount of heat exchange between theheat-receiving pipe main bodies 23 and the compressed fluid may beincreased, the length dimension of the heat-receiving pipe main bodies23 may be shortened, and thus the heat receiver 10A may be downsized.

For example, the pipe diameter of the heat-receiving pipe main bodies 23is 1.3 times that of the expanded section 20 e, the expanded section 20e is equipped with the heat transfer accelerator 20 h, and it istherefore possible to expand the amount of heat exchange by about 1.6 to2.4 times compared to an original pipe diameter.

Although the embodiments of the solar heat receiver according to thepresent invention have been described, the present invention is notlimited to the embodiments mentioned above. Additions, omissions,substitutions, and other variations may be made to the present inventionwithout departing from the spirit and scope of the present invention.The present invention is not limited by the above description, but onlyby the appended claims.

For example, in the present embodiment, although the shape of theexpanded section 20 c of the heat-receiving pipe 20 is substantially atrapezoidal shape when viewed from the side, the shape is not limitedthereto. For example, in the region in which the portion having the highheat flux (the high temperature section K) near the opening 11 b isincluded, a tapered shape which gradually spreads radially outward fromthe casing 11 toward the bottom or in an umbrella shape may be adopted.

Furthermore, the pipe diameter dimension of the expanded section 20 e ofthe heat-receiving pipe main bodies 23 having the large diameter in thesecond embodiment may be arbitrarily set, and may be determineddepending on the conditions such as the presence or the absence of theheat transfer accelerator as mentioned above.

In addition, the components of the embodiments mentioned above may besuitably replaced with well-known components, and the embodimentsmentioned above may be suitably combined with each other.

INDUSTRIAL APPLICABILITY

A solar light heat receiver includes a casing having an opening on whichsunlight is incident, and a plurality of heat-receiving pipes that arevertically arranged inside the casing and raise the temperature of aheat medium flowing therein by the irradiation of the sunlight. Theplurality of heat-receiving pipes are arranged so as to be spaced fromeach other and to extend in one direction. Centers of the respectiveheat-receiving pipes are arranged on the same circumference. Theplurality of heat-receiving pipes are bent outward in the radialdirection in a portion near the opening of the casing. Thus, a circlepassing through the centers of the plurality of heat-receiving pipes isconfigured so that a diameter in a region near the opening is expandedcompared to a diameter in a region separated from the opening.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

-   -   10, 10A: heat receiver (solar heat receiver)    -   11: casing    -   11 b: opening    -   11 c: expanded section    -   15: insulating material    -   20: heat-receiving pipe    -   20 a: front surface    -   20 b: back surface    -   20 c, 20 e: expanded section    -   20 h: heat transfer accelerator    -   23: heat-receiving pipe main body    -   D, d: pitch circle diameter    -   K: high temperature section

1. A solar heat receiver comprising: a casing having an opening on whichsunlight is incident; and a plurality of heat-receiving pipes which arearranged in the casing in a circumferential direction of the casing andthrough which a heat medium is circulated, wherein the heat-receivingpipes are configured so that portions having high heat flux on theopening side are extended to a radially outer position of the casing,expanded sections constituted by the plurality of heat-receiving pipesand having an expanded pitch circle diameter are formed, and thediameter of the heat-receiving pipe in the expanded section is greaterthan that of the heat-receiving pipe in a portion other than theexpanded section.
 2. (canceled)
 3. The solar heat receiver according toclaim 1, wherein a heat transfer accelerator is equipped inside theheat-receiving pipe in the expanded section.